In recent years, portable terminals including a touch panel-incorporated display panel have been increasingly popular as mobile phones or portable information processing terminals or the like. Such portable terminals (hereinafter, simply referred to as “portable terminals”) use a power-driven display device such as organic EL (electro luminescence), LCD (liquid crystal display), or LED (light emitting diode) as a display panel.
Many portable terminals are driven by battery and thus become inoperable when remaining battery power falls to or below a predetermined level. Therefore, reducing power consumption of such portable terminals is important to extend their continuously operable time.
Power-saving techniques relating to a display panel of a portable terminal are disclosed, for example, in PTL 1 and PTL 2.
The technique described in PTL 1 reduces, when no operation of a portable terminal is detected for a certain period of time, brightness of an overall display region (screen on a display panel) depending on the importance of an image being displayed. On the other hand, the technique described in PTL 2 identifies a region which is predicted to be continuously viewed by the user, based on the position of a cursor operated by the user, and reduces the brightness of regions other than the identified region.